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Interactions of prostaglandin A2 with the glutathione-mediated biotransformation system

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Author: Iersel, M.L.P.S. van · Cnubben, N.H.P. · Smink, N. · Koeman, J.H. · Bladeren, P.J. van
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Biochemical Pharmacology, 12, 57, 1383-1390
Identifier: 235060
doi: doi:10.1016/S0006-2952(99)00048-9
Keywords: Nutrition · Cells · Glutathione S-transferases · Inhibition · Metabolism · Prostaglandin A2 · 1 chloro 2,4 dinitrobenzene · Glutathione · Glutathione transferase · Prostaglandin a2 · Glutathione transferase P1 · GSTP1 protein, human · Isoenzyme · Prostaglandin A · Prostaglandin A2 · Biotransformation · Cell function · Cell metabolism · Cell proliferation · Controlled study · Cytotoxicity · Enzyme activity · Enzyme modification · Human · Human cell · Melanoma cell · Priority journal · Cell culture · Drug antagonism · Melanoma · Metabolism · Biotransformation · Glutathione · Glutathione S-Transferase pi · Glutathione Transferase · Humans · Isoenzymes · Melanoma · Prostaglandins A · Tumor Cells, Cultured


The cyclopentenone prostaglandin A2 (PGA2) is known to inhibit cell proliferation, and metabolism of this compound thus might be important in controlling its ultimate function. The glutathione-related metabolism of PGA2 was therefore investigated both with purified glutathione S-transferase P1-1 (GSTP1-1) and with IGR-39 human melanoma cells. Firstly, the irreversible inhibition of human GSTP1-1 and its mutants C47S, C101S, and C47S/C101S was studied. PGA2 appeared to inhibit GSTP1-1 mainly by binding to the cysteine 47 moiety of the enzyme. This binding was reversed by a molar excess of GSH, indicating that retro-Michael cleavage occurs. Secondly, after exposing IGR-39 human melanoma cells to PGA2, both diastereoisomers of the PGA2-glutathione conjugate are excreted into the medium, although with a clear excess of the S-form, due to its preferential formation by the GSTP1-1 present in the cells. Thirdly, the effect of PGA2 on intracellular GST activity was determined by quantification of the excreted glutathione conjugate S-(2,4-dinitrophenyl)glutathione (DNPSG) after exposure to 1-chloro-2,4-dinitrobenzene. DNPSG excretion was inhibited after incubation with 10 or 20 μM PGA2 for 1 or 4 hr, as a result of glutathione depletion, reversible GST inhibition, and covalent modification of intracellular GST. Furthermore, PGA2 also inhibited transport of DNPSG by the multidrug resistance-associated protein, an effect that was reversible and competitive. In conclusion, PGA2 modulates all three aspects of the glutathione-mediated biotransformation system, i.e. GSH levels, GSTP1-1 activity, and transport of GSH conjugates. A role for GSTP1-1 as a specific transport protein inside the cell is indicated. Copyright (C) 1999 Elsevier Science Inc.